A044180 Numbers n such that string 6,0 occurs in the base 7 representation of n but not of n-1.

42, 91, 140, 189, 238, 287, 294, 336, 385, 434, 483, 532, 581, 630, 637, 679, 728, 777, 826, 875, 924, 973, 980, 1022, 1071, 1120, 1169, 1218, 1267, 1316, 1323, 1365, 1414, 1463, 1512, 1561, 1610, 1659, 1666, 1708, 1757, 1806